Generally, the present development relates to systems and processes utilizing the repeatable characteristics of a magnetic stripe for authenticating stripe bearing objects, e.g., documents as credit cards.
Various forms of cards and other documents bearing a magnetic stripe have long been used for a variety of different purposes. Such magstripe cards are currently used in large numbers, for example in the forms of credit cards, debit cards, tickets, passes, I.D. cards and so on. Typically the magnetic stripes of such cards carry digitally recorded data, for example relating to the use of the card, the assigned user, and so on.
Although magnetic stripe documents are widely and successfully used in commerce and industry, various forms of copying have become common place. The aggregate losses from fraudulently copied magstripe cards are very large. Consequently, a continuing need exists for a practical and economical system and method to reliably identify, and thus verify or authenticate magstripe documents.
Over the years, there have been numerous proposals for verifying documents, including techniques for authenticating magnetic stripes. A substantial number of prior proposals have been based on a concept of using certain magnetic characteristics of the magnetic stripe to verify documents, as cards. In that regard, it has been determined that magnetic stripes possess inherent, substantially unique, magnetic characteristics that can be repeatedly sensed. Over the years, these characteristics have been recognized as contributing a signal component sometimes considered to be noise in the sensed analog signal. Thus, along with the sensed data, a repeatable signal component (noise) also is present. Essentially, just as the magnetic characteristics of individual stripes are distinct, the resulting “noise” signals are somewhat unique and can characterize or identify magnetic stripes. Thus, it has been proposed to employ such magnetic characteristics and the resulting “noise” signals as a basis for identifying and verifying individual magnetic stripe documents. In some instances, the general technique has been compared to the science of human fingerprinting, that is, involving the use of a somewhat unique physical characteristic for purposes of identification. However, although various verification techniques and structures, based on the noise or characteristic magnetic component of a sensed magstripe signal have been proposed, they have not been widely accepted.
One prior proposal involved using a separate non-data magnetic stripe placed on a document specifically for purposes of identifying the document. Other proposals have involved various treatments of the magnetic stripe, usually involving the signals that are recorded and sensed from magnetic stripes.
Typically, the magstripes on conventional magstripe cards are divided into parallel tracks that are digitally recorded and sensed. Many of the prior proposals for magstripe document verification have involved the record of one track of the magnetic stripe in the form of digital data represented by magnetic transitions along the length of the magnetic stripe. Portions of analog signals sensed from the magnetic track transitions, or other portions of the signal have been proposed for use in characterizing the card or document. For example, on a time base, peaks in the sensed analog signal (representing magnetic transitions) have been proposed for use in verifying the magnetic stripe. Other proposals have suggested using other portions of the sensed analog signal from one of the magnetic tracks. For example, the relatively flat signal portions representative of magnetized regions of the stripe (located between magnetic transitions) have been proposed for use.
Various techniques also have been proposed for attaining more consistent results in sensing the magnetic characteristic signals. For example, techniques have included: averaging the results of multiple sensings, oversampling (increased sampling as by a factor of one hundred) and using a phase locked loop to control sampling. It also has been opined that for identification and verification purposes, sizable variations are quite acceptable between individual sensings of magstripe characteristics.
In the final analysis, as indicated above, in spite of the numerous structures and techniques proposed for magstripe fingerprinting, the concept has not gained widespread acceptance. That is, using the so called “remanent noise” in a signal sensed from magstripes to verify individual documents has not come into widespread use. Rather, although numerous proposals have been suggested for such operation, the technique simply has not gained significant commercial or industrial acceptance.
Typically, magnetic stripe fraud involves variously copying the recorded data (including verification data) in either a digital or analog form and using it to verify a transaction. Thus, a considerable need exists for a reliable system of combating fraud related to magstripe documents, which fraud may involve various forms of copying, duplicating or misdirecting data.
In general, the system of the present invention is based on recognizing the various problems of using the repeatable characteristics of a magstripe for purposes of verification, for example, in broad commercial and industrial applications. In that regard, it has been determined that many problems arise in the arenas of broad industrial and commercial use which are not apparent in the laboratory.
One major consideration relating to the extensive use of magnetic characteristics for card verification involves the number of cards used in a system. For example, a commercial credit-card system may be required to accommodate many thousands of individual cards operating randomly in combination with hundreds, if not thousands, of individual processing units. Furthermore, in an extensive system, reliability becomes exceedingly important, particularly in the realms of financial and security transactions, as are involved with financial cards.
In general, the system of the present invention involves improvements that enable magnetic characteristic verification techniques to operate successfully and reliably in the realms of widespread commercial and industrial applications. Specifically, the processes and systems of the present invention are directed to developing reliable magnetic stripe verification in a large scale system.
As disclosed herein, repeatable magnetic characteristic signals (resulting from specific characteristic features of the magstripe) may be selected from defined areas of a digitally-recorded magnetic stripe. The defined areas may be located between magnetic data transitions. Such defined areas of the stripe may be magnetized to a level of saturation and accordingly produce relatively flat (stable) sections in the sensed analog signal. Although these signal sections are relatively flat, they manifest a low level signal (noise) representative of the repeatable magnetic characteristics or features of the stripe. Thus, such signal sections may be used to reliably characterize each magnetic stripe in a manner somewhat analogous to a fingerprint. As disclosed herein, further reliability is attained by testing signal amplitude and symmetry characteristics as well as challenging digital copies by excessive similarity tests involving recently sensed characteristics.
Regarding the basic characteristic determination, as disclosed herein, after sensing a magstripe to produce a magnetic analog signal (typically containing digital data) a target number of samples are taken from several relatively flat sections of the analog signal using a frequency lock loop. Individual samples in each group are converted to a digital form, then selectively processed to obtain a predetermined subset of samples. The predetermined subset of digitized samples is then further processed by offset selection to accomplish a sub-subset of digitized samples that become a component of a characteristic designation used for identification. That is, several sub-subsets of digitized samples are collected to form part of an identifier for the magstripe-bearing card.
With the magnetic characteristic resolved to a digital representation, dynamic range information is extracted from the digitized samples to supplement the magnetic characteristic in the representative identifier. In the disclosed embodiment, the dynamic range information is based on amplitude symmetry or waveform characteristics as disclosed in detail below. Generally, by including dynamic range information in the identifier for a magnetic stripe, certain forms of the copied identifier can be distinguished as disclosed in detail below.
Other methods of copying may present the identifier in a digital form, for example, in the ultimate form for the test comparison. As disclosed herein, such copying is challenged by comparing the presented identifier with recently sensed identifiers which are the likely source of copies. If the degree of similarity is excessive, copying is suggested. Otherwise, the freshly sensed identifier is tested by correlation with reference identifiers to verify the card or other document.